Abstract: The yellowing process is the unique step during yellow tea process, which causes the tea to change bright yellow in tea-infusion and tea-leaf colors. This study focused on the effects of leaf-temperature, moisture content, relative humidity and ventilation frequency on the formation of yellow-tea using the uniform raw fresh-leaves. In addition, the correlations of yellowing-process technological-factors and chemical constituents were analyzed. The results show that the ventilation frequency and relative humidity were the key factors for yellowing-process and quality improvement using the uniform raw fresh-leaves and under the traditional temperature and moisture content. The yellow tea quality would be improved by increasing ventilation frequency and relative humidity under traditional yellowing temperature and moisture content. The principal component analysis indicates that ventilation frequency and relative humidity had high correlation with many taste-constituents, including catechins CG, ECG, GCG, flavones Myr-rha, Que-gal, and amino acids theanine, Ser, Gln, Arg, His, GABA. The results indicates that yellowing-process factors influenced the mellow-, thick- and sweet-tastes of yellow tea by affecting the taste-chemical constituents. As a result, the following yellowing process parameters were suitable for preparation of premium yellow tea with the taste of mellow, thick and sweet: leaf temperature of (45±2)℃, leaf moisture content of (37±3)%, relative humidity of (80±5)%, and ventilation frequency of once per 10 min.

Key words: yellow tea, taste, quality, water factors, ventilation frequency